1. Field of the Invention
The present invention relates to a block polymer having a coating insulating portion and a conductive portion in its molecules, and a device using the polymer.
2. Description of the Related Art
Attention has been currently attracted to organic devices each using a conductive organic substance such as an organic semiconductor in association with the advance of the integration of electronic circuits. The organic devices have the following merits: the device can be bent, and, if a process for the production of the device from a solution becomes feasible, the device can be produced at a low cost, and is applicable to a process for the production of a large-area device. Examples of the organic semiconductor include low-molecular weight organic semiconductors such as pentacene, and polymeric semiconductors such as polythiophene. The polymeric semiconductors have been regarded as attractive conductive materials for the large-area process and the low-cost process because the devices have particularly good affinity for the solution process.
Although organic polymers are generally in the shape of a thread ball, a π-conjugated polymer such as a substituted polyacetylene, polydiacetylene, or polyphenylene ethynylene has generally a linear molecule. In addition, even a nonlinear polymer is not in the shape of a thread ball but in a shape close to an extended chain depending on its crystal structure or orientation state. Such a linear molecule, in particular, the π-conjugated polymer can be expected to function as a monomolecular electronic device in principle by joining both of its terminals to electrodes. The introduction of an alkyl chain as a side chain of the repeating structure of such a linear molecule suppresses the movement of carriers between the molecule and an adjacent molecule, so the carriers move linearly along the axis of the molecule. As a result, the distance along which the carriers move is equal to or shorter than the length of the molecule, so the device can operate at a high speed. In an ordinary organic device, carriers move according to a movement mode in which the carriers move along a molecular axis or a movement mode in which the carriers hops between adjacent molecules, and the movement according to the hopping movement mode becomes rate-determining. Accordingly, high-speed movement of the carriers can be realized by introducing an alkyl chain into the side chain to eliminate the intermolecular hopping movement mode. In addition, the introduction of an alkyl chain into the side chain has an improving effect on the solubility of the polymer.
In this case, the following problem is raised in the injection of carriers into an organic molecule. Since the conjugated polymer is surrounded by alkyl chains, the conjugate structure and each of the electrodes are insulated from each other. Accordingly, the injection of carriers into the conjugate structure is restricted even when the molecules are placed on the electrodes. Therefore, a technique for injecting a carrier into a conjugated polymer surrounded by alkyl chains is needed.
In addition, existing organic devices realize some degree of electrical junction based on physical contact established by depositing a metal onto organic molecules so that the metal serves as an electrode or by forming the organic molecules into a film on an electrode. However, the electrical junction at an interface between the molecule and the electrode has been regarded as a serious problem inherent in the organic devices.
In view of the foregoing, a technique for bonding a conjugated polymer and an electrode more strongly to suppress an influence of an interface between the polymer and the electrode on electrical junction has been needed.
A system utilizing a gold-thiol bond has been reported as a technique for bonding an organic molecule and an electrode. For example, Japanese Patent Application Laid-Open No. H06-163049 describes the application of a polymer with a thiol introduced into its side chains to an organic cell using in its electrode a conductive material obtained by introducing a thiol into a side chain of an acrylic polymer or methacrylic polymer.